Application of PIM for manufacturing WC-Co milling inserts

Abstract

The objective of this study is to examine the feasibility of manufacturing WC-Co milling insert by PIM process. WC-Co is used in a wide variety of cutting tools due to its high hardness, stiffness, compressive strength and wear resistance properties. WC-Co parts for a high stress application were conventionally produced by the press and sinter method, which were limited to 2 dimensional shapes. Manufacturing WC-Co parts for a high stress application by PIM implies that tool efficiency can be highly improved due to increased freedom in design. P30 grade WC powder (WC-Co-TiC-TaC system) was mixed with RIST-5B133 binder and injection molded into milling inserts (Taegu Tech. Model WCMX 06T308). The mean particle size of the powder was about 0.8μm. Injection molded specimens were debinded by solvent extraction and thermal degradation method at various conditions. The specimens were sintered at 1400°C for 1 hr in vacuum. Carbon content, weight loss, dimensional change, and macro defects of the specimen were carefully monitored at each stage of the PIM process. PIMed WC-Co milling inserts reached 100% full density after sintering. Its mechanical properties and microstructures was comparable with the press and sintered milling insert. Carbon content of the sintered WC-Co insert was mainly determined by the atmosphere of thermal debinding. By controlling powder loading and injection molding condition, dimensional accuracy could be obtained within 0.4%. We confirm that PIM can not only be an alternative manufacturing method for WC-Co parts economically but also provide a design freedom for more efficient cutting tools.